The prediction of earthquakes is a relatively new branch of
seismology. Just two decades ago, earthquake prediction was not even
considered to be serious science; rather, it was left to astrologers,
mystics, and religious zealots (Press & Siever, 1978). The
emergence of earthquake prediction as a truly scientific discipline
has taken place as a result of a program of fundamental observations
begun in the late 1960's and supplemented in 1973 and 1976. The
research effort has from its inception in the United States consisted
both of attempts to develop a systematic catalog of precursory
phenomena through field measurements and a program of fundamental
studies of the physical basis for the occurrence and nature of
earthquakes and of the pre-earthquake failure process (Raleigh,
1980).

Earthquake premonition by animals, while having a long history and
persistence in literature, does not seem to fit into the rational
world of science, and as a phenomenon, it has the added disadvantage
in that it cannot be examined at will. Skepticism of anomalous animal
behavior before earthquakes by many scientists in the Western world
is largely based upon this unfavorable image, as any scientist
interested in studying this problem risks not only his or her
professional reputation, but also any chance of getting research
funds (Tributsch, 1982). Beginning in the mid-1970's, however, the
perspective of the possible connection between animals and
earthquakes began to change, when it was revealed that in 1975, China
successfully predicted a major earthquake, using observations of
abnormal animal behavior, as well as geophysical and geochemical
precursors. The entire population of Haicheng, a large city, was
evacuated before a magnitude 7.3 earthquake struck, saving thousands
of lives. This imminent prediction was the first such prediction of a
major earthquake in recorded history. U.S. seismological teams
visiting China were impressed by China's methods and accomplishments
in earthquake prediction, although the Chinese admitted some failures
among their successes, and much more study still needs to be done. In
1976, the U.S. Geological Survey sponsored a conference on "Abnormal
Animal Behavior Prior to Earthquakes", held in Menlo Park,
California. This conference discussed and reviewed accounts of
unusual animal behavior and the various geophysical precursors which
might stimulate the animals. In 1979, a second U.S.G.S. conference
was held at the University of Texas in Galveston. This conference
introduced experimental data on the effects of earthquake-related
geophysical and geochemical phenomena on animals, under controlled
conditions. A survey, summary, and analysis of the literature
concerning abnormal animal behavior before earthquakes, and its
possible usefulness in predicting future earthquakes, is the focus of
this paper.

CHAPTER 1
ANECDOTAL EVIDENCESources of Data

The oldest recorded observations of abnormal animal behavior
connected with earthquakes date back some 3000 years, a continuous
record containing an estimated 50 millions words in the official
dynasty records of China. However, their usefulness to modern
scientists is somewhat limited by the sheer volume of material, and
by the style of ancient classical Chinese writing - it is not certain
whether the observed unusual behavior took place before or after the
earthquakes (Lee et al., 1976).

Although many examples of unusual animal behavior have been
reported from nearly all parts of the world, many scientists have
regarded them as anecdotal folklore concocted by untrained observers,
and not to be taken seriously (Lee et al., 1976). Nearly all reported
accounts of abnormal animal behavior are second-hand, that is, told
by laymen observers to scientists after the earthquake occurred
(termed "retrospective recollections"), and thus are subjective
interpretations which may be inaccurate or exaggerated. Attempts have
been made by Lott et al. (1977, 1979, 1980) to introduce more
rigorous controls on data collection methodology; behavioral
specialists collected eyewitness accounts of several earthquakes with
carefully worded questions (the respondents were not pressured to
answer).

A different direction of investigation was started by biologists,
biophysicists, and animal behaviorists. Their laboratory studies of
the effects of geophysical and geochemical phenomena known to be
present prior to earthquakes provided new experimental data of animal
sensitivities to these stimuli under controlled conditions. (Many of
these studies were initially concerned with isolated phenomena not
necessarily related to earthquakes, such as the effect of sound waves
on fish.)

A major difficulty of relating abnormal animal behavior to
earthquakes is that unlike mechanical measuring devices, the behavior
of animals is not well understood. Also, the behavior of the many
types of animals in the data is not uniform, either between
individuals of one species or between groups of different species.
Finally, abnormal animal behavior may also be caused by non-seismic
"noise" factors such as weather, magnetic storms, disease, insects,
or other conditions causing stress in animals (McClellan, 1980).

Therefore, any meaningful analysis of the literature must consider
these questions:

1. How reliable is the data?
2. Can non-seismic noise factors be eliminated from the data set of a
particular earthquake?
3. What is the "normal" behavior of animals under non-earthquake
conditions?
4. Can a particular geophysical stimulus be shown to cause the
observed behavior?
5. What are the sensory thresholds (limits of detection by the
senses) of the animals under study to different stimuli?
6. How many individual animals within a population tend to be more
sensitive to the earthquake phenomena?

Anecdotal Accounts

By far, the largest volume of data concerning abnormal animal
behavior before earthquakes consists of innumerable anecdotal
observations made by laymen, classified as folklore or legends (Lee
et al., 1976). The earliest accounts date back several thousand years
to the time of Pliny the Elder in Rome, and to the Chou Dynasty
(circa 1000 B.C.) in China. However, folklore accounts have long been
ignored as irrelevant by scientists, as expressed by Richter (1958)
in Elementary Seismology :
"...The legendary material of seismology includes many stories of
horses and other domestic animals being uneasy during the hours
preceding a large earthquake. It is impossible to judge such evidence
scientifically. If there is any explanation beyond coincidence and
incomplete reporting, it probably rests on the occurrence of small
foreshocks, not noticed by humans, but disturbing to sensitive
animals. During earthquakes, animals are seen to react as they do to
almost any sudden and unexpected event." (Foreshocks are defined as
small tremors that commonly precede a larger earthquake by an
interval ranging from seconds to weeks, and that originates at or
near the focus of the larger earthquake.)
Rikitake (1976) believes that while not all of these legends may be
true, it is nevertheless important for scientists to look into things
which might contain some truth, without being biased. Lee et al.
(1976) compiled a summary of literature on this subject, (some of
which was translated from foreign journals not readily available in
the Western world), which they organized into three geographical
sections: China, Japan, and Western countries, as the history and
approach towards studying the problem is somewhat different in each
of these three regions.

Chinese Data on Animal Behavior Anomalies

Modern records suggest that China endures the most severe seismic
activity on earth. Because the majority of major tremors strike
densely populated areas, their impact has been more lethal than in
most other countries. China averages six quakes of at least 6.0 on
the Richter scale each year, whereas the United States averages two
or three per year, most of them in the Aleutian Islands of Alaska.
Thus, the philosophy of China's government is to include as much
information as can be gathered to aid in prediction, including the
abnormal behavior of animals (Mead, 1976).

Earthquakes have played an important role in China's political
history. The emperors of the ancient dynasties were said to have a
"mandate from Heaven" to rule, on the condition that the emperor was
benevolent to his subjects. The regimes of many a corrupt emperor
were toppled by the civil unrest caused by the destruction of a great
earthquake, as the suffering peasants symbolically interpreted the
earthquake as a sign from Heaven that "the emperor had lost his
mandate," and revolted. The belief that great earthquakes herald a
change in the nation's leadership is still widely held in China even
during modern times, as the 1976 Tangshan earthquake happened to
occur just months before the death of Chairman Mao Tse-tung. The
Tangshan earthquake killed more than half a million people;
unfortunately, a short-term prediction could not be made, although a
long-range earthquake forecast had been made for that area of China.
For political as well as practical reasons, the Chinese have been
using animal anomalies as one of the key indicators to predict
earthquakes. With over 80% of the population living in farming areas
in close association with animals, this approach has great public
appeal (Lee et al., 1976). In 1966, spurred by two severe earthquakes
which struck Hsingtai, the government of China mobilized its
citizenry and declared a "People's War" on earthquakes, by way of a
program of scientific research, education of the general population,
and the construction of a nationwide seismic monitoring network
(employing 10,000 professional seismologists and 20,000 technicians
and amateur observers) overseen by a National Bureau of Seismology,
with the goal of successfully predicting future earthquakes. The
effort has been described as the "Chinese equivalent of the American
Apollo space program (Mead, 1976)."

The following accounts of abnormal animal behavior before
earthquakes in China, Japan, and the Western world will concentrate
mostly upon descriptions, and not on their possible causes, which
will be discussed in a later chapter:
Historical records said that farmers in China could tell that
something was vastly wrong in the earth beneath them when normally
placid horses reared up and ran away. Dogs howled continuously for no
apparent reason. Fish leaped from the water into the air. Animals
which normally hid from humans, such as snakes and rats, suddenly
appeared in droves (Mead, 1976). Cattle, sheep, mules, and pigs
refused to enter their corrals. Frightened pigeons flew continuously
and refused to nest. Rabbits raised and twitched their ears
spasmodically, jumped aimlessly and bumped into things. Most
dramatically, hibernating snakes left their burrows early, sometimes
in the dead of winter, only to freeze to death on the icy ground (Lee
et al., 1976).

From Lee et al., (1976) the following observations of abnormal
animal behavior before an earthquake were recorded at the Tientsin
Zoo by the Chinese government:

A giant panda refused to play and was observed holding its head
with its forearms, crying strangely. A tiger became depressed and
sluggish. Loaches (a type of bottom-dwelling fish), leeches, and
turtles suddenly swam up and down and rolled over continuously. A
Tibetan yak refused to eat, and rolled over continuously on the
ground. Water-loving birds such as ducks and swans stayed on land far
away from the shore, avoided the water, and pointed their feet
towards the sky. Among large zoo animals, those with young were
observed to be more sensitive to earthquake precursors than those
without young.
More observations were recorded in historical Chinese documents (Lee
et al., 1976): sudden calls of pheasants, abundant catch of fish,
disappearance of rats, fish jumping from the water onto the shore,
bees building their nests in low places, cocks crowing at night,
disappearance of cats, dogs barking loudly and continuously, birds
singing at night, normally placid catfish swimming actively, and
snakes and rabbits moving their homes.

In addition, the Geological Bureau of China in 1975 reported that
these animals also behaved anomalously before earthquakes (Lee et
al., 1976): tigers, wolves, deer, eels, frogs, donkeys, geese,
monkeys, sparrows, eagles, and insects. People living in areas near
the earthquake epicenter observed that burrowing animals such as rats
and snakes, etc. were more sensitive than animals living above the
ground, and small animals appeared to be more sensitive than large
animals. According to the survey of four major regions of China by
the combined team from the Biophysics and Zoology Institutes of the
Academia Sinica, preliminary results (dated 1975) show that 58
species of wild and domestic animals have relatively reliable
anomalous reactions before earthquakes.

About one and a half months before the February 4, 1975 Haicheng
earthquake (magnitude 7.3 on the Richter scale), hibernating snakes
came out of their underground burrows and froze to death. One or two
days before the earthquake, pigs refused to eat, climbed up the walls
of their stalls, and butted the doors. Small pigs bit each other, and
a dozen or so small pigs chewed off their tails and ate them. Cows
became restless, pawed the ground, fought with each other and butted
horns. Deer at a deer farm suddenly ran madly, trying to escape from
their pens. One deer reportedly broke two of its legs while running
away in a panic (Lee et al., 1976). Birds at a municipal aviary
attempted to relocate their nests; while carrying their eggs, many of
them fell to the ground and broke. Many caged birds, such as
sparrows, attempted to fly inside their cages, as if trying to
escape; many died from injuries suffered from striking the sides of
their cages (Deng and Jiang, 1981).
To summarize the above accounts, the Group of Earthquake Research of
the Institute of Biophysics, Academia Sinica (1979) made the
following analysis of the data:

Table 1A, Table 1B
Figure 1
Figure 2

1. Most animals in the seismic area become increasingly restless, and
a number of them fall into a state of anxiety.

2. These features may appear from a few minutes to as long as ten
days before the earthquake, but usually the precursor time is within
24 hours of the quake.

3. These phenomena appear to have a non-random and non-uniform
regional distribution, occurring mostly in particular belts of the
seismic area and in certain regions. These places correlate to some
degree with the strike of active faults, as well as with the bends,
branches or terminal points of faults. It appears that they tend to
be in the epicentral area or high- intensity zones of the impending
earthquake (Fig. 1).

5. Although there is great variety in the cases of unusual
behavior, generally speaking, this behavior falls in to the category
of increased restlessness - being startled, extremely nervous, and
panicky, as if the animals were on the brink of meeting their natural
enemies. A small number of animals may become depressed or apathetic.

6. Macroscopic (detectable without instrumentation) changes in
animal behavior constitute only one of many precursors of
earthquakes. Some characteristics, such as precursor time, regional
distribution, animal species, total number of events per day, etc.
are linked with origin-time, the epicentral location and the
magnitude of the coming quake. So far as the time of occurrence is
concerned, it can be used as a means of extremely short-term
forecasting. Combined with data from other disciplines, animal
observations may be of some value in making an overall judgment.

7. Anomalous animal behavior has also been noticed during the
earthquake, as well as before.

8. The number of animals of any given species that behave
abnormally prior to earthquakes is not necessarily a high proportion
of the total population (usually, only a fraction of a given species
shows unusual behavior). Some show no anomalous behavior; on the
other hand, some anomalous animal behavior may not be followed by an
earthquake. Furthermore, it must be noted that much of the data were
collected after the earthquakes had occurred.

9. The unusual behavior is not necessarily related only to
earthquakes. Non-seismological factors can sometimes cause similar
behavior. Although such interfering factors have been investigated,
it is almost impossible to eliminate them completely.

Japanese Data on Animal Behavior Anomalies

Ancient Japanese legends attributed earthquakes to giant catfish
moving underground (Fig. 3), a tradition said to have started
sometime in the eighteenth century. After that time, some examples of
catfish associated with earthquakes were reported in historic
documents. In particular, many colored wood-block prints with catfish
legends appeared after the 1855 Edo earthquake. During the late
1800's, J. Milne described some examples of unusual behavior of fish
before earthquakes, but no remarkable scientific work was done until
the 1920's (Lee et al., 1976).

The Kanto earthquake of 1923, which destroyed much of Tokyo, led
several seismologists to pay attention to the problem of animal
anomalies. For example, in 1932, Hatai and Abe investigated the
responses of the catfish, Parasilurusasotus to
earthquakes. During that same year, Hatai, Kokubo and Abe studied
earth currents in relation to the response of catfish. Terada in 1932
demonstrated an apparently good correlation between the number of
fish caught and the number of earthquakes felt near the time of the
1930 Ito earthquake swarm. More than 20 examples of unusual behavior
of fish and sea life were reported by people on the coast of Japan,
as well as several

Figure 3
examples of unusual behavior of rats and birds. Musha in 1935
summarized a great deal of data on unusual animal behavior and
earthquakes (Lee et al., 1976).

After the 1930's, however, research on animal behavior in Japan
gradually diminished. Possible reasons are: (1) World War II
intervened, (2) no large destructive earthquake has occurred in Japan
since 1949, and (3) no scientific progress in the mechanism of animal
anomalies has been advanced. More recently, Japanese scientists
renewed their interest in unusual animal behavior and earthquakes,
especially after the Chinese success in predicting the Haicheng
earthquake of February 4, 1975 (Lee et al., 1976).

Most of the animal anomalies reported in Japan are concerned with
fish. This is not surprising, because 80% of Japanese earthquakes
occur in the oceanic areas surrounding Japan, and fish are a staple
food for the Japanese. Some of the more dramatic accounts regarding
fish and marine life describe sudden changes of habitat: crabs and
catfish crawling out of the water onto land, deep sea fish swimming
upwards to surface waters and being caught by fisherman, dolphins
appearing offshore, and the discovery of benthic (bottom-dwelling)
diatoms and mud in the stomachs of sardines, which normally ingest
planktonic diatoms (Lee et al., 1976).

During the period 1913 to 1916, Omori conducted experiments to
determine the ability of pheasants to detect earth tremors. Working
in a quiet house where he could hear pheasants crowing in a
neighboring garden, he took note of the time of every perceptible
earthquake and comparing it with the crowing of the pheasants and
also later checking the tromometer, an instrument for recording
minute earth tremors. In 11 out of 23 cases, the pheasants were
actually more sensitive than Omori; they either crowed before the
scientist felt the quake, or crowed when he felt no quake but found
that one had been registered by the instruments. Passing vehicles
which shook the ground did not cause the pheasants to crow (Anderson,
1973).
Since most animal anomalies observed in Japan are based on
second-hand reports, their accuracies vary greatly. Japanese
reviewers of this subject tend to collect all available information
regardless of accuracy (Lee et al., 1976).

Western Data on Animal Behavior Anomalies

The semi-scientific literature of the Western world contains many
anecdotal reports of supposed animal responses to forthcoming
earthquakes. Most of the reports on record were made during the
nineteenth century; they are so far separated culturally and in time
from the more objective present-day reports that little credence can
be given to them (Lee et al., 1976). Perhaps the best known of all
animal-earthquake stories dates back to the early twentieth century;
the dogs of San Francisco were reported to have barked the night
before the great earthquake struck the city in the early morning of
April 18, 1906 (Anderson, 1973). Cats also became very excited during
the San Francisco earthquake. Some ran around wildly with their fur
standing on end; others hid in dark corners or behaved abnormally in
other ways. In some cases, they disappeared for several days after
the quake. During the aftershocks, cats seemed to register the
tremors before people did. They cowered in fear and ran. Cows were
reported fleeing in a panic before the earthquake; some were seen
lowing and mooing during the earthquake. Horses snorted, trembled,
and galloped in a frightened panic (Tributsch, 1982).
Von Hentig (1923) summarized the following observations which were
reported without reference to particular earthquakes in the older
literature:
1. Dogs bark frantically, howl, growl, or whine. Dogs and foxes are
restless, whine and howl, and rush into the open; or they are
lethargic, somnolent, and either hide or stay by their masters. Cats
draw back ears, bristle fur, and mew pitifully.
2. Pigs and other animals show signs of suffering for 10 days prior
to an earthquake; pigs bite each other like dogs.
3. Swallows abandon nests and seek refuge under roofs on the eve of
an earthquake.
4. Fish flee from the banks toward the center of rivers; fish migrate
strangely.
5. Mice, rats, moles, lizards and snakes leave burrows and wander
restlessly.
6. Alligators vocalize loudly, leave the water and seek refuge in the
woods.
Werner (1974) mentions these observations in one of the few Russian
reports available on abnormal animal behavior before earthquakes:
ants pick up their eggs and move out of anthills in a mass migration,
pheasants crow, goats and antelopes refuse to go into indoor pens for
months before earthquakes, while tigers and other big cats do the
same several weeks before earthquakes. Additionally, it was reported
that a dog saved its master's life by dragging her out of the house
before a large 1966 earthquake struck, and the natives of Kamchatka
were said to observe the behavior of bears to predict volcanic
eruptions. There were also reports of a dramatic surge in complaints
of heart patients prior to a 1948 earthquake. To Russian scientists,
this suggested that human hearts can somehow detect small variations
in geophysical factors such as static and magnetic fields caused by
the buildup toward an earth tremor, and implied that the same natural
device may also warn animals.
In April and May of 1976, there were earthquakes of magnitude 7 in
the Uzbek Soviet Republic. One day before the catastrophe, great
swarms of bats were observed flying around the day. (Bats are
normally nocturnal.) Such observations have also been made in Turkey
(Tributsch, 1982). Tributsch (1978) reported the following unusual
animal behavior which occurred before the May 6, 1976 earthquake
epicentered in Friuli, Italy:

According to Tributsch (1978), this type of behavior was
essentially identical to that reported from China.
Tributsch (1982) summarized the essential information from the
following folk legends, which, if valid, would indicate an imminent
earthquake:
(1) when four-legged animals show great nervousness without apparent
reason (Peru, Venezuela),
(2) when birds become excited and give forth unusual calls
(Peru),
(3) when dogs howl in unison (Chile),
(4) when roosters crow persistently at night (Italy, Chile),
(5) when roosting chickens leave theirs roost and cackle excitedly
(Chile),
(6) when wild animals appear to be tame and intimidated (Chile),
(7) when normally abundant flies suddenly disappear (Venezuela),
(8) when snakes leave their lairs and flee outdoors (Cuba),
(9) when birds flock together, fly high, and circle conspicuously
(Greece),
(10) when bears leave their winter lairs prematurely (Kamchatka,
U.S.S.R.),
(11) when cats cry nervously, run around houses excitedly, and then
flee outdoors (Italy, Chile).

In many respects, the above list resembles accounts reported in
China (Tributsch, 1982). Tributsch (1982) believes that folk wisdom
about earthquake prediction by animals deserves respect. Many of the
popular sayings are, after all, not just the fruits of individual
observations, but have been repeatedly submitted to tests through
generations. It would be senseless and pointless for people who
depend so much on nature to observe the animals for no apparent
purpose or benefit. It seems unlikely that China's thousands of years
of tradition, and the earnest efforts and observations of hundreds of
millions of people would be devoted to the apparition of a phantom.
Yet to Western scientists, the lack of explanation of the mechanisms
behind these phenomena seems sufficient enough reason to reject the
folklore altogether, despite evidence that some of these observations
can be understood and used to predict earthquakes (Tributsch,
1982).

CHAPTER 2
PATTERNS IN THE ANIMAL BEHAVIOR PHENOMENA

Context of Abnormal Animal Behavior

From the voluminous historical catalog of anecdotal observations of
animal behavior, certain essential patterns may be found. Most
unusual animal behavior is not totally abnormal for the animal's
repertoire, but has been observed in the species under other
circumstances (Table 2); in other words, the behavior is only
"abnormal" when it occurs out of its normal context. Since
earthquakes are relatively rare events, it is unlikely that animals
have evolved a specific instinctual response to pre-earthquake
signals; thus, it is speculated that animals may misinterpret various
geophysical changes and respond in a confused, but frightened manner.
The behavior sometimes resembles startle movements in response to a
sudden stimulus; in other cases, it resembles the orientation
movements that animals use to investigate or avoid a stimulus
(Buskirk et al., 1981). The behavior reported in post-earthquake
interviews resembles fear or escape reactions and ranges from mild
response to bizarre behavior (Lott et al., 1980). Investigators
familiar with the full range of behavior for a species will often
recognize that reported "abnormal" behavior is actually
species-typical behavior which may be triggered by a variety of
stimuli not necessarily related to earthquakes. For example, behavior
such as cats hiding and pigs biting their tails also appears during
times of stress unrelated to geophysical changes (Buskirk et al.,
1981).

Much of the behavior resembles that reported for animals before
geophysical events other than earthquakes, such as thunderstorms or
sudden volcanic eruptions. For instance, dogs sniffed and pawed at
the earth two to four days prior to the eruption in 1955 of Mt.
Kilauea, Hawaii (Buskirk et al., 1981). Cows abandoned their pastures
two weeks before Volcan Arenal, Costa Rica erupted in 1968, and dogs
barked incessantly for minutes to hours prior to the 1965 eruption at
Tall, Philippines (Anderson, 1973).

Table 2

Time Patterns of Abnormal Animal Behavior

For a few major earthquakes, reports of unusual animal behavior have
been widespread enough that it was possible to study the timing of
the behavior (Fig. 4). For the Tangshan, China, earthquake (M = 7.8,
July 28, 1976), reports of fish, rodents, and wolves were cited as
early as a month or two before the event. In the epicentral area of
Tangshan, over 70% of the reported incidents took place within 1 day
before the earthquake. Most incidents (70%) also occurred in areas
which were to experience the great Mercalli intensities (Buskirk et
al., 1981). Although in other earthquakes, unusual behavior of cows
and horse has been noted in the seconds or minutes prior to the shock
(Lee et al., 1976; Tributsch, 1978), at Tangshan only 10% of the
reported incidents for horse, donkeys, and cows occurred immediately
before the earthquake. At Tangshan there were reports of earthquake
lightning and changes in telluric currents the days before the
earthquake, but there were no reported foreshocks (Buskirk et al.,
1981).

Figure 4

As early as a month prior to the 1975 earthquake in Haicheng, China,
unusual behavior in fish, rodents, and snakes was observed. However,
most of the unusual behavior took place within two days of the main
shock. Numerous foreshocks and obvious groundwater changes also
occurred 1 or 2 days before this event (Buskirk et al., 1981).

Rikitake (1978) considered the temporal relationship between
geophysical and behavioral precursors for the Izu, Japan, earthquake
(M = 7.0, January 14, 1978), shown in Fig. 5. Nearly all physical
precursors measured for this and other earthquakes occurred at least
2 days prior to the main shock, while most of the 129 behavior
incidents happened within 24 hours of the earthquake (Fig. 6). Most
behavioral precursors coincided with a swarm of foreshocks a few
hours prior to the main shock (Rikitake, 1978).

Rikitake's statistical analysis (1978) attempted to compare the
nature of animal precursors to those obtained by geophysical and
geochemical methods. He classified these precursors within three time
frames: long-range (measured in years), moderately short-range
(measured in days), and extremely short-range (measured in hours).
The conclusions of the statistical analysis are outlined as follows:

Figure 5, Figure 6
1. No long range animal precursors having times on the order of years
(long-range) have been reported.
2. Most of unusual animal behavior seems to belong to moderately
short-range precursors which have a mean precursor time amount to 0.4
day, if they are indeed precursors at all. If this conclusion is
true, it can be said that animal precursors are complementary to
geophysical ones, that is, the distribution of animal precursors
exhibits a maximum around 0.4 days. Meanwhile, the frequency
distribution of geophysical precursors indicates a minimum around
that value. Although it is not certain whether or not the above
conclusion is a mere coincidence, it seems worthwhile to pay
attention to abnormal animal behavior which might have a spectrum of
precursor times different from that of geophysical precursors (Fig.
7, 8, and 9).
3. It seems likely, as far as the existing data are concerned, that
animals sometimes present extremely short-range premonitory signals
on the order of a few hours, just like some geophysical disciplines
such as land deformation, resistivity, underground water, and so on
(Fig. 10 and 11). No significant difference in precursor time
distribution between geophysical and animal precursors is found as
far as the extremely short-range precursors are concerned.
Figure 7
Figure 8
Figure 9
Figure 10, Figure 11
4. The existing data on unusual behavior prior to an earthquake
indicate that animal precursors cannot be ruled out although most
data are based on non-scientific observations. Although no firm proof
that animal behavior reflects signals forerunning an earthquake has
been established, it is not fair to rule it out in the search for
earthquake precursors (Rikitake, 1978).
The great variability of animal behavior before earthquakes is
apparent from post-earthquake interviews such as the standardized
studies of Lott et al., (1979). Individual animals of the same
species, even when located in the epicentral area, did not respond in
the same way before the 1977 Willits, California, earthquake (M =
4.7) (Lott et al., 1979).
This variability has two sources: behavioral differences among
individual animals, even within the same species, and geophysical
differences between earthquakes (Buskirk et al., 1981). Earthquakes
have individual characteristics: modifications occur in acoustic
waves, air pressure levels, tilt of the land, electrical
conductivity, electromagnetic fields, electrostatic discharges, gas
emissions, groundwater level, and temperature, for example, but these
events do not always appear in identical patterns. The time of onset,
frequency, duration, and magnitude of each may vary, as well as which
particular physical events are present. Often, the physical changes
are so small that they fall within the range of normal fluctuations
regularly experienced by the animal (Shaw, 1977). In addition, it is
clear from comparative studies (Lott et al., 1980) that unusual
behavior is observed before some earthquakes but not others. The same
type of interview study was conducted after four California area
earthquakes which occurred during the late 1970's: Willits, November
22, 1977 (M = 4.7); Landers, March 15, 1979 (M = 5.5); Coyote Lake,
August 6, 1979 (M = 5.4); and Mexicali, October 19, 1979 (M = 6.9).
All four had strike-slip faults with rather shallow epicenters
located in rural areas. Only the Willits earthquake had a significant
number of behavior precursors (Lott et al., 1980).
Figure 12 (Buskirk et al., 1981) displays available data for 36
earthquakes on four continents. The following generalizations may be
made about the reported unusual animal behavior:
1. Most, but not all, of the animal behavior precursors occur close
to the epicenter within 1 or 2 days of the earthquake. The species
primarily reported are domestic mammals, such as dogs, probably
because of their close association with humans, and animals of
commercial importance, such as horses and chickens (Buskirk et al.,
1981).
2. Some, but not all, of the behavior precursors occur within a few
minutes before the earthquake (Tributsch, 1978, 1982). For these
precursors, it is difficult to dismiss the hypothesis that the
animals are sensing the vibrations of the P waves arriving from the
earthquake,
Figure 12
while humans sense only the latter and stronger S waves or surface
waves (Buskirk et al., 1981). (Animals such as horses and pheasants
responded about 5 to 10 seconds before humans felt the earthquake in
an aftershock sequence in Chile.) However, phenomena that may
coincide with the P wave arrival are placed in a separate category
from earlier behavior precursors by some researchers (Rikitake, 1976;
Lott et al., 1979).
3. A few of the behavioral precursors actually are reported days to
weeks before the earthquakes, and some of these occur at a
considerable distance from the epicenter (Buskirk et al., 1981). The
animal species most often mentioned in these reports are fish
(Rikitake, 1976) and rodents (Lee et al., 1976).

CHAPTER 3
OVERVIEW OF POSSIBLE SENSORY MECHANISMS IN ANIMALS

Several problems complicate an analysis of reports concerning
anomalous animal behavior prior to earthquakes: the variability of
animal behavior, the unreliability of human observations, and the
existence of uncontrolled physical factors such as weather
(McClellan, 1980). These problems are so significant that scientists
have taken a serious look at the phenomena only recently. During the
late 1970's and early 1980's, several types of investigations were
undertaken to document the nature of animal behavior responses
(Buskirk et al., 1981). These investigations include systematic
post-earthquake interviews (Lott et al., 1979), a network of
observers reporting by telephone (Otis and Krautz, 1980), and
biological activity monitors on individual animals under controlled
conditions in a field laboratory (Kenagy and Enright, 1980; Lindberg
et al., 1981).

Because anecdotal observations are unable to explain the
mechanisms of what the animals might be sensing prior to an
earthquake, Frey (1980) advocates the use of psychophysical and
psychophysiological tests on the animals in the laboratory, where
geophysical events and stimuli might be recreated. In the final
analysis, the animal is simply a measuring device. The measuring
devices used by humans, such as tilt meters, are nothing more than
extensions of our own sensory systems which are acting as measuring
devices. From the anecdotal reports, it would appear that the animals
are measuring something that we are either not measuring or, are
interpreting the stimuli differently than we are (Frey, 1980).
Buskirk et al. (1981) compared available data on geophysical
precursors to the sensory thresholds of humans and other animals
(obtained from laboratory studies), particularly those mentioned in
the anecdotes. Much of the published biological research relevant to
this area of study is unfamiliar to most geophysicists, and the gap
between the biological and geological disciplines was bridged
somewhat by the U.S.G.S. Conferences on Abnormal Animal Behavior
Prior to Earthquakes, held in 1976 and in 1979. For example, the
second U.S.G.S. conference reviewed biological and biophysical
research on: detection of sound and vibration by birds (Kreithen,
1980); vibrotactile responses in animals and man (Verrillo, 1980);
low frequency vibration detection in fishes (Fay and Patricoski,
1980); seismic wave detection by fishes (Frohlich and Buskirk, 1980);
electric and magnetic field detection by animals (Kalmijin, 1980;
Medici, 1980; Frey, 1980); changes in air ions on animals before
earthquakes (Yost, 1980); and earthquake odor detection by animals
(Moulton, 1980).
Buskirk et al. (1981) cited a number of geophysical phenomena that
have been observed prior to earthquakes might also stimulate unusual
animal behavior, including:
(1) sound with an intensity and frequency outside the range of human
perception,
(2) variations in local magnetic or electric fields,
(3) ground vibrations or foreshocks,
(4) changes in groundwater level,
(5) electromagnetic waves, and
(6) the release of gases usually trapped beneath the surface.

Animals probably do not sense some types of reported geophysical
precursors, including ground tilt, variations in the velocities of P
and S waves, changes in electrical resistivity, and gravity anomalies
(Buskirk et al., 1981).

CHAPTER 4
ANIMAL SENSITIVITIES TO GEOPHYSICAL STIMULI

Buskirk et al. (1981) attempted to correlate the biological
literature on animal sensitivities to geophysical stimuli commonly
reported prior to earthquakes. To strengthen their correlations, they
considered (1) the background level of the stimulus, (2) data from
the geophysical literature suggesting that the stimulus may occur
occasionally as an earthquake precursor, and (3) biological research
(in summary form) on the sensitivity of animals to that type of
stimulus.

Sounds and Vibrations (Foreshocks)

Before discussing these studies, it is pertinent to mention some
basic background information regarding acoustics and human
hearing:
Sound is created by the movement of energy through a medium, such as
a gas (air), liquid (water), or solid (rock), which causes it to
vibrate as a pressure wave. The speed of vibration (usually measured
in cycles per second, or Hertz, abbreviated as "Hz") is called the
frequency. The size of a wave cycle, or wavelength, has an inverse
relationship with the frequency. The measurement unit of sound
pressure level (loudness) is usually the decibel, abbreviated "dB."
Because the perception of sound is not linear, but logarithmic, a 10
decibel increase in sound roughly corresponds to double the loudness.
It has been demonstrated that human hearing is not linear in its
perception of the frequency spectrum. While the range of human
hearing extends from 20 - 20,000 Hz, the ear is more sensitive to the
mid-range frequencies (from above 100 Hz to about 10,000 Hz), and
weak at the lower and upper frequencies. Very low frequency sounds
(below 20 Hz) are usually not heard, but felt, while sensitivity to
high frequencies drops off sharply past 15,000 Hz; with age, this
loss of sensitivity is more pronounced. Also, there exists a
relationship between the frequency range of sound, the energy
required to produce it, and its ability to travel through a medium.
High frequency sounds have shorter wavelengths, and thus require less
energy to produce them. Because they tend to travel in a straight
line, their relatively low energy is easily absorbed by obstacles
(high frequency seismic sound waves would be attenuated by
surrounding rock). Low frequency sounds are more energetic, travel in
a radiating pattern (rather than a straight line), are less prone to
attenuation, and can travel great distances. Seismic waves commonly
have a frequencies between 0.01 and 10 Hz (Buskirk et al., 1981).
Biologists have shown that many species of animals possess a greater
frequency range of hearing (down to as low as 1 Hz, or as high as
100,000 Hz), and a greater sensitivity in the ranges where human
hearing is poor. If sounds are indeed generated before earthquakes,
animals which are sensitive to either very low or very high
frequencies may be hearing something that humans cannot detect
(Buskirk et al., 1981).

Background levelsAnimals that can sense low-amplitude sounds or vibrations are
exposed to many types of earth noise below 100 Hz in frequency. If
unusual animal behavior is caused by foreshocks, then the seismic
signals must somehow differ from background noise because of its
frequency, amplitude, or pattern. Several kinds of earth noise have
been measured. Microquakes have a predominant frequency lower than 1
Hz. Infrasound (ultra-low frequency sound below 50 Hz) generated by
thunderstorms has the highest sound pressure levels at frequencies
below 100 Hz. Microearthquakes in active seismic areas create a
low-level background noise at frequencies below 50 Hz. Man-made
noises by machines also have been shown to contribute to background
noise in many locations; many of these sounds reach as low as 5 Hz
(which can be detected by pigeons). However, most of these man-made
sounds are extremely regular in amplitude and frequency content,
quite unlike earthquake-related sounds (Buskirk et al., 1981).

Acoustic Precursors and Coseismic SignalsSounds that precede or accompany the shaking of the ground have
been reported for a number of earthquakes in the literature (Buskirk
et al., 1981).
Because more than 4000 seismograph stations are currently operating
throughout the world, foreshocks are probably the most commonly
observed precursors of large earthquakes. Although not all
earthquakes have detectable foreshocks, their existence provides a
reasonable explanation for much of the observed unusual animal
behavior. According to Buskirk et al., (1981) at least 60% of major
earthquakes (M > 7.0) had foreshocks large enough (M > 4.0) to
be located by the International Seismological Centre (Fig. 13).
Buskirk et al. (1981) addressed an important misconception concerning
foreshocks and precursory animal behavior. It is often incorrectly
assumed that sound waves below the human hearing threshold (i.e.
below about 50 Hz) cannot explain the animal behavior because these
signals would be detected by seismographs. In fact, for two reasons
it is quite possible that foreshocks which stimulate unusual animal
behavior often are not detected by seismographs. First, conventional
seismographs are most sensitive to frequencies around 0.01 - 10 Hz,
and most of the energy radiated by microearthquakes and especially by
microfractures is at much higher frequencies. Second, in
well-instrumented areas, conventional seismographs routinely detect
earthquakes with magnitudes as small as 1.5, but as is shown in
Figure 13 and Table 3, over most of the earth's surface, earthquakes
as large as M = 4 routinely go undetected. Thus, many foreshocks
detectable by animals may go undetected by existing seismic networks
(Buskirk et al., 1981).
Sound is produced in all major earthquakes (Fig. 14); the seismic
waves themselves (0.1 - 10 Hz), the microquakes (up to several
hundred Hz), and the sounds produced by breaking rock (up to 3000
Hz). The latter source of sound was confirmed by laboratory
experiments on rock fracturing; before rocks break, fine hairline
cracks appear. In this process, ultrasound signals are emitted at
frequencies that can reach 100,000 - 1,000,000 Hz. The frequency
varies with the size of the tears that are being produced and thus
with the kind of rock in which the cracks appear. However, most of
this high frequency sound is selectively muffled by the surrounding
rock, leaving mostly the lower frequency earthquake sounds to escape
to the earth's surface (Tributsch, 1982).
Audible earthquake sounds with frequencies of 40 to 70 Hz were
fortuitously tape recorded in 1975 in the Imperial Valley of
California (Hill et al., 1976). These authors calculated that P waves
could account for audible sounds a few seconds before the perceptible
S waves for small earthquakes. While earthquakes can generate
low-frequency pressure waves (infrasound) which can travel great
distances, higher frequency sound waves (audible to humans and
animals) are attenuated by the rock overlying the
Table 3
Figure 13
Figure 14
earthquake focus. Instruments sensitive to very low frequency
infrasound (0.1 - 5 Hz) recorded such sounds from the 1964 Alaska
earthquake as far away as Washington, D.C. In addition, loud noises
resembling thunder have been reported days to months before
earthquakes, even in the absence of foreshocks (Buskirk et al.,
1981).

Sound Detection By AnimalsIn reviewing animal sensitivity data, Buskirk et al. (1981)
divided the sound spectrum into three ranges: below 100 Hz, 100 -
10,000 Hz (the range of best human sensitivity), and above 10,000 Hz.
Most of the data reviewed are from tests performed by biologists
involving behavior responses of animals to a sound stimulus.
According to Buskirk et al. (1981), it is unlikely that sounds in the
frequency range 100 - 5000 Hz are responsible for the anecdotes about
unusual animal behavior, because in this frequency range, most
animals are no more sensitive than humans (Fig. 15). Within this
range, common animals such as cats and dogs are generally more
sensitive than humans above 5000 Hz. The most sensitive mammals are
no more than an order of magnitude more sensitive than humans in this
frequency range (Buskirk et al, 1981). Some birds, such as owls, have
more sensitive hearing than man in the mid-frequency range of 1000 -
10,000 Hz, a threshold of 10 decibels below the normal 0 dB reference
for human hearing (Kreithen, 1980).
Figure 15
Above 10,000 Hz, human hearing is clearly inferior to that of many
small mammalian species. Behavioral as well as neurophysiological
data show that laboratory mice and rats are extremely sensitive to
sounds in the range 30,000 - 80,000 Hz. These rodents "speak" to each
other within this frequency range, probably at close range, since
ultrasound over 20,000 Hz tends to attenuate very quickly with
distance. In anecdotal observations, some of the rats in a nearby
cage displayed frightened behavior before rock failure during
laboratory tests (Buskirk et al., 1981).
Although many mammals are more sensitive than humans in this
high-frequency range, sounds of this frequency are probably not the
cause of the unusual animal behavior observed before earthquakes.
Only rather small cracks (with lengths of a few centimeters or less)
would produce sounds with most of their energy at frequencies above
10,000 Hz. If the cracks are small, the amount of energy they radiate
is also small. In addition, it has been calculated that these
high-frequency sounds would attenuate too quickly to explain abnormal
animal behavior before earthquakes (Buskirk et al., 1981). Similarly,
Hill (1976) showed that attenuation would prevent animals from
sensing most foreshocks that produce ultrasounds. Animals could
perceive such high-frequency signals only from earthquakes with
depths shallower than 0.01 km (Hill, 1976).
One of the best candidates for explaining observations of unusual
animal behavior before earthquakes is infrasound (sounds below 50 Hz
in frequency). A number of studies of birds and mammals show that
many animals respond to extremely low sound pressure levels at
frequencies far below 50 Hz (Buskirk et al., 1981). Kreithen (1980)
showed that birds are highly sensitive to low frequency sounds and
vibrations, and their ability to analyze complex signals far exceeds
the ability of humans (Fig. 16). The general capacity of birds to
filter signals buried in noise may exceed the abilities of our best
instruments. Pigeons have low frequency auditory responses down as
low as 3 cycles per minute (0.05 Hz). Their infrasonic sensitivity is
40 - 50 dB better than most other animals, including man (Kreithen,
1980). Furthermore, pigeons are able to discriminate between very
small frequency differences (as low as 3%) in the range 1 - 20 Hz;
for example, pigeons can tell the difference between a 2.00 Hz and a
2.06 Hz signal. This means that a flying bird can determine the
direction of a very long wavelength sound merely by performing a
slight detour in its flight path. The ability to use doppler shifts
may not be crucial for earthquake detection, but it does point out
that pigeons have a precise ability to process low frequency signals
(Kreithen, 1980).
Birds possess three types of vibration receptors: (1) skin receptors
in the legs and elsewhere, which decode surface vibrations and are
most sensitive between 400 - 800 Hz, (2) inner ear receptors, which
include organs which provide a horizontal reference plane for the
bird's head, and (3) semicircular canals, with a fluid-filled chamber
which is very
Figure 16
Figure 17
sensitive to angular accelerations and are responsible for the bird's
balance (Kreithen, 1980). In laboratory experiments, pigeons who had
parts of their inner ears surgically removed were unresponsive to
infrasound, while unaltered pigeons were visibly frightened (Buskirk
et al., 1981). Birds have a very different pattern of sound and
vibration sensitivity than do humans. Birds can "hear" ground
vibrations as low as 2 Hz (whereas humans can only hear down to 20
Hz); below 2 Hz, birds feel rather than hear the vibrations. For
frequencies between 0.5 and 20 Hz, birds are from one to two orders
of magnitude more sensitive than man, as shown in Figures 16 and 17
(Kreithen, 1980).
Buskirk et al. (1981) also cited kangaroo rats as being more
sensitive than humans to infrasound. Whereas pigeons may use
infrasound as homing signals, kangaroo rats may detect this sound to
escape from predators.
Most earlier investigations of animal perception of
earthquake-generated sounds concentrated on mammals, and did not
consider aquatic species, or discuss low frequency sounds. However,
Frohlich and Buskirk (1980) extended the analysis of Hill (1976) and
considered data collected from fish. They concluded that fish could
sense earthquake-generated pressure waves at least 2 Richter
magnitudes smaller than those detectable by humans. In addition, an
extrapolation of these hearing curves indicates that fish sensitivity
to seismic sounds becomes increasingly better than human sensitivity
as the frequency gets lower (Buskirk et al., 1981).
Fish are apparently more sensitive than most mammals to infrasound
(50 Hz and below). They possess different sensory organs for
perceiving sound: (1) the lateral line system, which is an array of
hair cells extending along the side of the fish, apparently most
sensitive to frequencies 200 Hz and below; (2) the inner ear otolith,
located in the fish's skull; and (3) the air-filled swim bladder.
Besides the greater hearing and vibration sensitivity of fish, their
aquatic environment efficiently propagates sound and seismic waves,
with relatively little attenuation. Seismic waves travelling through
water are several orders of magnitude more intense than similar waves
travelling through air, because water is a denser medium. Experiments
have shown that fish can also discriminate low-level seismic signals
from background noise (Frohlich and Buskirk, 1980).

Vibration Reception By AnimalsA number of animals possess various sensitive external organs
which detect ground vibrations directly, independent of their sense
of hearing. The vibration detection capability of humans has been
more carefully studied than those of any other animal, so they
provide a good comparison with animal studies (Buskirk et al.,
1981).
Humans are able to detect mechanical vibrations, using skin receptors
occurring on the body, covering a range from below 1 Hz to over
100,000 Hz, which far exceeds the range of human hearing. The most
sensitive receptors are located in the fingertips or the eardrum;
their sensitivity is comparable to most other mammals. However,
because humans seldom have their fingertips or their eardrums in
contact with the ground, they cannot detect earthquake vibrations
felt by terrestrial and burrowing animals of comparable sensitivity
(Buskirk et al., 1981).
Recalling the anecdotal reports from China of snakes leaving their
burrows more than a month before a major earthquake (Lee et al.,
1976), these phenomena may be explained by evidence that snakes are
physiologically more sensitive to low frequency vibrations below 100
Hz, even more so in the range below 10 Hz (Buskirk et al., 1981).
Chinese investigators have also reported tests in which the skin
mechanoreceptors of 50 pigeons were severed, while the same number in
a control group were left intact. Prior to a small earthquake, the
normal pigeons panicked and flew around, while the altered birds
behaved as usual (Lee et al., 1976).
Buskirk et al. (1981) cited a number of studies on insects, in which
they reported much greater sensitivities to vibrations relative to
humans.
In summary, the biological literature indicates that many animals are
more sensitive to sounds and vibrations than man, in terms of
frequency range, threshold response, and noise-filtering capacity. In
view of the tests in different frequency ranges, low-frequency
infrasound seems to be the best candidate among acoustical precursors
detectable by animals before earthquakes, because it is less likely
to be attenuated by the surrounding rock. However, as pointed out by
Tributsch (1982), since dogs, cats, rats and mice are no more
sensitive to infrasound than are humans, their panic reactions
preceding earthquakes cannot be accounted for by infrasound.
Electromagnetic Phenomena

Electromagnetic phenomena which occur prior to an earthquake
include: electric fields (changes in the earth's background level),
changes in the geomagnetic field, electromagnetic radiation caused by
electrical phenomena in rock, and the creation of air ions (Buskirk
et al., 1981).
Any electric and magnetic precursor within the animal's sensitivity
and frequency range is a potential agent in evoking anomalous
behavior in advance of earthquakes. Since there is no evidence of
adaptive behavior in response to precursor phenomena, the animals
that do respond seem either to misinterpret the stimuli or exhibit an
inappropriate normal behavior. As animals are likely to detect
precursor phenomena, the study of anomalous behavior may very well
contribute, if only indirectly, to the geophysicist's ability to
forecast earthquakes (Kalmijin, 1980).

Electric Field ChangesThe earth's level of background electric fields varies
considerably in time and in space. Local electrical storms, rainfall,
and magnetic storms can cause large fluctuations. Measurements of
electric field changes prior to earthquakes stand above background
variations. The mechanisms behind these electrical changes have been
attributed to: increased ionization due to the release of radioactive
radon gas, or by the movement of groundwater (Buskirk et al.,
1981).
Aquatic animals show extraordinary sensitivity to weak direct current
electric fields, with thresholds well below electric fields reported
before some major earthquakes (Fig. 18). Electric fish such as the
elephant fish (freshwater Gymnarchidae ) and electric
catfish have specialized organs which can detect minute electrical
changes in the water (Buskirk et al., 1981). Sharks can home in on
prey in the absence of any odor cues, using their well-developed
electrical sensitivity. Catfish, rays, and eels also possess this
ability (Tributsch, 1982).
A correlation between catfish activity and electrical earthquake
precursors has been reported by Japanese researchers. During the
1930's, Hatai and Abe observed the catfish Parasilurusasotus in an aquarium filled with water flowing in from a
freshwater creek. Several hours before a small earthquake, the fish
became unusually sensitive to tapping on the table on which their
aquarium rested. Fluctuations in the electric field were measured in
the creek corresponding to the time of the catfishes' reactions. When
the water flow (and the electric field fluctuations) from the creek
was cut off, the catfish were no longer able to "predict" earthquakes
(Buskirk et al., 1981).
Among terrestrial animals, mice, monkeys, and hamsters have been
exposed to artificially manipulated electric fields (Fig. 18).
Hamsters have been shown to be very sensitive to electric field
changes. In laboratory experiments, hamsters were allowed to
comfortably establish their nests in glass terrariums; then, an
external electric field was alternated at irregular intervals,
simulating the changes in a thunderstorm. The behavioral changes were
remarkable; the hamsters wandered aimlessly from nest to nest
(Tributsch, 1982). Changing electric fields are believed to affect
nerve membranes, hormones, enzymes, and electrical activity in the
brains of animals (Buskirk et al., 1981).
In general, terrestrial animals are much less sensitive (by about 4
or more orders of magnitude) than aquatic animals to electric field
changes. It thus seems unlikely that terrestrial animals would
respond to the levels of electric fields reported prior to
earthquakes (Buskirk et al., 1981). Rapidly alternating electrical
fields seem to have the most effect on land animals, whereas slowly
changing electric fields would be significant only if they departed
greatly from the background level (Tributsch, 1982).

Magnetic Field ChangesA major problem in interpreting the significance of animal
response to magnetic changes is the great spatial and temporal
variation in the earth's magnetic field. The normal geomagnetic field
strength is 0.5 gauss, or 50,000 gammas. Typical temporal
Figure 18
Figure 19
variations in the field are about 30 gammas. Most geomagnetic changes
associated with most recent earthquakes have been no greater than
about 20 gammas (Rikitake, 1976).
Some animals respond to extremely small changes in the magnetic
field, including some changes of the order of those observed before
some earthquakes (about 10 gammas). However, Buskirk et al. (1981)
have concluded that it is unlikely that magnetic field variations
cause unusual animal behavior before earthquakes. The documentation
of animal response to changes in magnetic field is of three types:
the impairment of normal orientation movements of moving animals
during short-term magnetic fluctuations, the response of stationary
animals to the reversal or cancellation of the geomagnetic field, and
changes in animal behavior occurring during exposure to larger
artificial fields. The greatest sensitivities to magnetic changes has
been demonstrated in experiments concerning animal orientation or
homing. As indicated in Fig. 19, several species, including migrating
birds, homing birds, and honeybees, have been shown to respond to
magnetic changes as small as 10 gammas. However, as the chart shows,
documented geomagnetic changes fall below the range of sensitivity of
most animals (Buskirk et al., 1981).
In summary, magnetic field changes are probably not detected by
animals before earthquakes because of the following:
1. Magnetic precursors are extremely small, about 20 gammas or less.
Biological evidence indicates that such small changes are either
undetectable or just barely detectable by animals.
2. Normal cyclical variations in the geomagnetic field, along with
changes due to storms, are in the range of 20 gammas or so. This
makes it difficult to tell whether the magnetic changes are due to an
impending earthquake.
3. Magnetic precursory changes tend to occur over a period of days or
weeks, while animals are more likely to respond to changes over
minutes or hours. Therefore, there is little synchronicity of
magnetic changes and abnormal animal behavior (Buskirk et al.,
1981).

Microwave And Other Electromagnetic RadiationAlthough microwave radiation has been mentioned as a possible
cause of unusual animal behavior before earthquakes (Frey, 1980), no
mechanism that produces microwaves during an earthquake has been
proposed, and there are no published field data on microwave
precursors. In addition, even if microwaves were produced in the
hypocentral region of an earthquake, it is difficult to see how they
could be transmitted to the surface, since the earth is opaque to
microwaves (Buskirk et al., 1981).
Soviet scientists during the early 1980's reported that broadband
electromagnetic radiation signals occurred prior to 12 shallow focus
earthquakes located at distances of up to 1000 km away from the
detecting devices. These precursors occurred from a few hours to a
week before the earthquake (usually 1 to 2 days before), and were not
detected prior to any earthquakes with a focus deeper than 30 km.
Some Soviet scientists believe that this is a type of ionization
phenomena which originates in the atmosphere above the epicentral
region of shallow earthquakes, caused by some electromechanical or
electrostatic mechanisms in the earth's crust, and may also explain
"earthquake lights" (Buskirk et al., 1981).
The body of information about the biological effects of long-wave
electromagnetic radiation is still full of gaps. Nevertheless, it can
be assumed with some certainty that the long waves can have effects
on living creatures that are at least as great as those caused by the
much weaker rapid alternating electric fields (Tributsch, 1982).
Symptoms of depression, insomnia, and general malaise have been
reported by workers after being exposed for several hours daily in
the radiation field. Migratory birds were reported to have flown off
course because of the effect of a powerful transmitting antenna set
up by the U.S. Navy; this antenna used extremely low frequency radio
waves to communicate with submerged submarines. Therefore, long-wave
electromagnetic radiation from the ground should not be completely
eliminated as a possible earthquake precursor detectable by animals
(Tributsch, 1982).

Phenomena Related To Air IonsFor terrestrial animals mentioned in the anecdotal reports,
changes in the density of air ions (electrically-charged particles)
may cause strange behavior. Tributsch (1982) believes that these
charged aerosol particles are more abundant prior to earthquakes, and
may explain other phenomena as well, such as earthquake lightning and
earthquake fog.
Electrostatic phenomena are observed during earthquakes and may be
implicated in precursory animal behavior (Yost, 1980). The release of
charged particles into the atmosphere prior to an earthquake could
cause significant changes in the ambient levels of small air ions
(Table 4), which many organisms may be capable of detecting. (Large
air ions are believed to be biologically inactive.) Biological
literature contains many reports of air ions influencing animal
behavior under laboratory conditions, but caution must be exercised
when extrapolating these results to the field. Ambient ion levels are
strongly influenced by weather, which could modify or mask any ion
changes due to earthquakes (Yost, 1980).
Several mechanisms which may produce air ions before earthquakes have
been postulated, although few have been tested in the field (Table
5). Radon outgassing of the soil near earthquake faults is believed
to be responsible for a 50 - 100% increase in the background level of
ions present. Such outgassing may begin several weeks before an
earthquake, and the rate of outgassing may reach two or three times
the normal background level. This could be caused by movement of the
water-mineral interface in the soil, which creates an electrostatic
release of positive charge into the air. Another mechanism proposed
is a piezoelectric effect due to rocks placed
Table 4, Table 5
under stress in the fault zones, which can create a large release of
charge (a result confirmed in laboratory stress tests of granite and
ceramics). However, the high conductivity of the soil would probably
absorb this charge (Yost, 1980).
Some of the anecdotal reports of abnormal animal behavior (Lee et
al., 1976) resembles similar reactions reported by biologists who
studied the effects of excessive levels of positive ions. Positive
ions seem to inhibit test performance of laboratory rats (Yost,
1980), increase susceptibility to disease in mice, and retard growth
in microbes (Buskirk et al., 1981). Long-term depletion of ions and
an excess of positive ions can cause physiological changes and a
heightened emotional state in animals. In mammals, an excess of
positive air ions is known to increase the level of the neurohormone
serotonin, which causes irritable behavior, changed habits, and
physiological deterioration. Weather-sensitive humans possess high
serotonin levels during periods of hot, dry winds, when high levels
of positive ions are measured. Their symptoms include headaches,
tension, and swelling. These symptoms disappear when humans are
exposed to antistatic treatments, or high levels of negative air ions
(Buskirk et al., 1981). Commercial negative-ion generators have been
sold during the past few years, claiming to produce physiological and
psychological well-being by removing the deleterious positive air
ions from the living and working environment. The "good smell" of air
after a rainstorm is due to the presence of large amounts of negative
ions, which has a soothing effect (Tributsch, 1982).
Under certain geological and atmospheric conditions, positive
airborne ions (charged aerosols) seem to appear in abundance before
an earthquake. Some typical individual behavior patterns can simply
be interpreted as the animals' flight responses before charged clouds
of particles streaming out of the ground. If such clouds appeared
before earthquakes and penetrated the burrows of snakes, mice, and
other small animals, it would explain their flight from underground.
The agitation and flight of birds could also be explained by airborne
clouds of positive ions. It also explains why so many different
animals are reported to have fled any enclosed buildings - enclosed
spaces possess much higher charge densities than open areas, and the
animals seek to escape the electrostatic effects which must cause
them great discomfort (Tributsch, 1982).
In summary, air ions are still a possible candidate to explain
unusual animal behavior prior to earthquakes. However, with the
geophysical and biological data available at present, it is not yet
possible to make a quantitative interpretation of these phenomena
(Buskirk et al., 1981).

Phenomena Related to the Opening or Closing of Small CracksChanging stress conditions near the hypocentral region can open
or close tiny cracks prior to the occurrence of an earthquake,
changing the permeability of nearby aquifers, affecting groundwater
levels, and affecting measures of electrical resistivity. In
addition, the opening of cracks can influence the rate of release of
gases contained within the earth (Buskirk et al., 1981).

Precursory Changes in Groundwater LevelIrregular water levels, artesian flow, and muddy wells have been
correlated with many historic earthquakes, and reportedly were used
extensively in predicting the 1975 Haicheng, China, earthquake (Group
of Earthquake Research, 1979). In the epicentral area of Haicheng,
wells became artesian 12 hours before the earthquake, and had been
muddy and oily the previous day. Waterspouts, muddy wells, floods,
and interruptions in the flow of hot springs had been reported within
50 km of the epicenter within the previous month (Buskirk et al.,
1981). In a study of water table changes in the area of San Andreas,
California, small but significant water level minima were followed by
earthquakes on the fault, while no significant water level changes
were associated with two more distant earthquakes. Striking changes
in well levels are most commonly observed one or two days before
earthquakes (Rikitake, 1978). Unfortunately, a great many water level
variations result from seasonal changes and short-term changes caused
by rains. Rains also affect measurement of tilt, electrical
resistivity, and radon concentration (Rikitake, 1976).
The presence of groundwater changes seems to correlate with anomalous
animal behavior during the 3 months before the 1975 Haicheng, China,
earthquake in an analysis by Deng and Jiang (1981). From the
geographical spacing and timing of the data within 150 km of the
epicenter, there appears to be a clustering of the two types of
anomalies, with perhaps a slight lag in the animal behavior
observations. Both the number of groundwater changes and the reports
of abnormal animal behavior began to increase dramatically on the day
of the first recorded foreshock, 3 days before the magnitude 7.3
earthquake (Deng and Jiang, 1981).
It is possible that groundwater changes of seismic origin could
explain a few observations of unusual behavior in animals with
burrows or nests underground; for example, snakes emerging from
hibernation in midwinter and rats moving their dens (Lee et al.,
1976). However, these groundwater changes are often small, and it is
therefore difficult to predict how they could affect animal behavior.
In addition, many of the behavioral anomalies could also be caused by
other stimuli, such as the presence of odorous gases. Furthermore,
changes in water level of non-seismic origin occur commonly without
affecting animal behavior. For these reasons, it seems unlikely that
groundwater changes could explain unusual animal behavior before
earthquakes (Buskirk et al., 1981).

Earth GasesChanging stress conditions which open tiny cracks in rocks before
an earthquake may change the release rate for gases trapped beneath
the ground. Measurements of radon concentration in soil gases and in
groundwater provide the strongest evidence that gases are released
before earthquakes (Buskirk et al., 1981).
There are several difficulties with using radon anomalies to predict
earthquakes. Radon changes which accompany earthquakes cannot always
be attributed solely to changes in tectonic stress, because rainfall
and seasonal climate changes also affect radon levels, as shown in
Fig. 20 (Buskirk et al., 1981).
Although radon is easily measured because of its radioactivity, other
gases are also released, such as hydrogen sulfide, ozone, and
phosphorus. In Japan, the levels of elements such as helium, argon,
nitrogen, fluorine, iodine, mercury, and uranium in groundwater were
observed to change prior to earthquakes. Prior to the earthquake in
Haicheng, China, the precursory changes in the levels of dissolved
nitrates, sulfates, chloride, and fluoride in groundwater were
reported (Buskirk et al., 1981).
Figure 20

Gaseous OdorantsHistorical accounts from different parts of the world reported
unusual smells before earthquakes. Many of these events coincided
with unusual animal behavior (Moulton, 1980), often resembling animal
responses to strange smells, such as dogs barking and sniffing the
air (Buskirk et al., 1981). Before the 1975 earthquake in Haicheng,
China, citizens in the epicentral area reported smelling unusual
odors such as sulfides, phosphorus, and ozone about a month or two
before the earthquake. Just before the earthquake, there was a dense,
stratified fog with a strange odor, and dogs were seen sniffing and
digging in the snow (Tributsch, 1982). These sulfurous odors are most
likely to include one or more of the following: hydrogen sulfide,
carbon disulfide, cobalt sulfide, sulfur dioxide, and dimethyl
sulfide (Moulton, 1980). Tributsch (1982) speculates that electrical
phenomena before earthquakes may electrolyze groundwater and create
new chemical compounds which animals smell, but do not recognize, and
cause reactions of fear. This hypothesis may explain why non-seismic
emissions of gases from the earth (such as swamp methane) do not
cause the same reactions from animals who encounter the gases
(Tributsch, 1982).
If we wish to examine the question of whether animals smell gases
that leak out of the ground before earthquakes and are alarmed by
them, we must take note that all living things except apes and most
birds have a keener sense of smell than man, as
Figure 21
shown in Fig. 21. Compared to humans, dogs have a sense of smell
roughly one million times more sensitive. Male silk moths are able to
detect a single air-borne molecule of pheromone (a sexual attractant)
secreted by female moths over a range of 7 miles (Tributsch, 1982).
However, the measurement of olfactory thresholds is complex, and it
is difficult to compare different species quantitatively. Laboratory
tests of olfactory sensitivity on dogs were inconclusive, because
naturally-occurring odorants could not be used, as they made
decontamination of the test chambers difficult (Buskirk et al.,
1981).
The behavior of fish prior to earthquakes is also consistent with
known behavior responses to olfactory stimuli observed in other
circumstances. Eels, minnows, catfish, and trout seem to have a sense
of smell equal to or better than humans. Homing and orientation
movements of salmon, eels, and bullhead catfish apparently require
chemical cues. Alarm behavior is triggered by chemicals released from
the injured skin of other fish, especially those of the same species.
This fright behavior is prevalent only in the Ostariophysini
species of fish which are mentioned most often in the anecdotes
(Buskirk et al., 1981). Deep sea fishes and bottom-dwelling fishes
have been reported to behave strangely before earthquakes (Moulton,
1980). Moulton (1980) believes that sulfides or other odorants may be
released into the seawater prior to earthquakes, especially if there
is a
fault zone or hydrothermal vent nearby. In quantitative terms,
however, it is difficult to compare the sense of smell in fish to
that in land animals (Buskirk et al., 1981).
Given that most animals possess better olfactory sensitivities than
humans, the release of odorous gases before earthquakes seems to be a
good candidate for some behavioral anomalies in animals (Buskirk et
al., 1981).

Humans usually report animal behavior before earthquakes as being
unusual only if they themselves sense no precursory stimuli. In order
to isolate the causes of the animal behavior, it is therefore
necessary to identify those precursory stimuli which are detectable
by animals, but not by humans. Among the geophysical precursors
discussed in the previous chapter, the most promising candidates
include: (1) infrasound (audible low-frequency sound of about 10 - 40
Hz) and ground vibrations, (2) electric field changes, (3)
positively-charged aerosol particles, and (4) earthquake gases
smelled by animals. It must be noted that none of these stimuli alone
can explain all of the observed behavioral anomalies in animals
(Buskirk et al., 1981; Tributsch, 1982). Also, Tributsch (1982) notes
that not all geophysical stimuli cause the reaction of fear in
animals. Each of the four geophysical factors listed above will be
discussed and compared in an attempt to find which one(s) best
explain abnormal animal behavior before earthquakes.

Audible Low-Frequency Sound/Ground VibrationsSeveral quite diverse species, including birds, rodents, and
fish, are known to respond to sounds with frequencies of about 40 Hz
and below that are 2 to more orders of magnitude weaker than those
detectable by humans. Animals can also detect foreshocks about 2
Richter magnitudes smaller or correspondingly more distant than those
detectable by man (Buskirk et al., 1981).
Stierman (1980) and a team of seismologists from the California
Institute of Technology recorded two moderate (M = 4.9 and 5.2)
earthquakes, followed by an earthquake swarm, in the Mojave Desert in
March of 1979. Their field observations noted that many small
earthquakes generated audible booming noises, which was accompanied
by the barking of dogs. Stierman noted that the dogs responded to
virtually every booming noise by a brief but vigorous sequence of
barking about 4 to 10 seconds after the shock (the dogs did not bark
before the noise). In several cases, the dogs responded to a seismic
aftershock not felt or heard by the human observers, but was recorded
by their seismograph. Stierman speculated that the vibrations
generated by small foreshocks would be misidentified as thunder by
animals dwelling underground. If thunderstorms typically signal
spring rains in a region, for hibernating animals (snakes, frogs,
worms, etc.), seismic vibrations which mimic thunder could cause
their untimely awakening (Stierman, 1980). Foreshocks are the most
probable explanation for reports of unusual animal behavior that
occurs very far from the epicenter (Buskirk et al., 1981). Many of
the distant behavior reports concern fish, particularly in Japan (Lee
et al., 1976). The relatively low attenuation of sound waves
propagating in water may allow seismic waves from foreshocks to
travel greater distances through water than through air (Frohlich and
Buskirk, 1980).
It has been shown in laboratory studies that sounds in the 100- to
5000- Hz range are detected nearly as well by humans as by animals;
therefore, it is unlikely that seismic sounds caused by foreshocks in
the mid-range frequencies can explain their unusual behavior.
Although many animals are much more sensitive than humans to
high-frequency sound above 5000 Hz, it is also known that higher
frequency seismic sounds are easily attenuated within a short
distance from the earthquake hypocenter (Hill, 1976).
Depending upon the species, below a certain threshold frequency, low
frequency vibrations are no longer heard, but felt. For this reason,
ground vibrations may be overlapped with audible low frequency sounds
and treated as more or less a single geophysical precursor.
Frequencies from about 50 Hz and below may collectively be called
infrasound. A number of animal species, including fish, snakes,
birds, rodents, and insects, are much more sensitive than humans to
vibrations in the 10 - 100 Hz frequency range. It is important to
note that seismographs are most sensitive in the 0.1 - 10 Hz range,
meaning that animals may respond to earthquake shocks having
frequencies from 10 - 100 Hz which are not recorded by seismographs.
Although humans possess the capability to feel seismic vibrations
through the palms of their hands and the soles of their feet, this
requires close contact to the ground, which is an unnatural
situation. Also, humans rely mostly on eyesight, and tend to ignore
vibrations sensed by animals, who use vibrations to find food or
avoid predators (Buskirk et al., 1981).
The advantages of citing infrasound for explaining anomalous
pre-quake animal behavior are:
1. Infrasound is capable to travelling great distances without
appreciable attenuation, which explains abnormal animal behavior
which occurs far from the earthquake epicenter.
2. It accounts for the anomalous behavior of underground and
burrowing animals, such as snakes and rats, who flee their hiding
places often months before the earthquake occurs.
3. It accounts for the anomalous behavior of fish and other sea
creatures, who generally are much more sensitive to low frequency
vibrations, which propagate with greater speed and intensity under
water than in air (Frohlich and Buskirk, 1980).

Infrasound does not explain, however, the panic reactions of dogs,
cats, and other mammals that are not appreciably more sensitive than
humans to low frequency vibrations . Also, birds in the branches of
trees are unlikely to feel the intensity of seismic vibrations felt
in the ground (Tributsch, 1982).

Electric Field ChangesAlthough many animals have been found to be quite sensitive to
small changes in electric fields, there is laboratory data on only a
few species. What is currently known about this area is that aquatic
animals, such as sharks and some other fish, are much more sensitive
than land animals to electric field changes. However, electric field
changes before earthquakes have seldom been documented, and those
were measured only on land (Buskirk et al., 1981). According to
Buskirk et al. (1981) it seems unlikely from available data that
animals can sense changes in electric fields before earthquakes.

Positively-Charged IonsThe effects of positively-charged ions on animal physiology and
behavior have been well documented. An excess of airborne cations
(positively-charged aerosols) can cause general irritation and
excitability in animals, evidenced by a measurable increase in the
body levels of serotonin (a powerful neurohormone affecting sleep,
moods, and the transmission of nerve impulses), which is known to
cause such reactions (Tributsch, 1982). Tributsch (1982) favors this
hypothesis for explaining abnormal animal behavior before
earthquakes. The following observations and circumstantial evidence
are in favor of citing charged aerosols as the culprit for pre-quake
animal behavior:
1. The unusual behavior of flying birds (who would not feel seismic
vibrations as intensely as ground-dwellers), and the abandonment of
enclosed shelters (which hold distressful concentrations of static
charges) by animals such as cats may be explained by electrostatic
charging of the air.
2. Shortly before the 1976 earthquake epicentered in Friuli, Italy,
Tributsch observed an anomalous electrostatic phenomenon in a
watchmaker's shop - the watchmaker was unable to repair a watch
because the small stainless steel parts kept jumping apart from each
other, implying that they had somehow acquired the same electrical
charge (like charges repel each other). The metal objects could only
have acquired this charge by charged aerosol particles expelled by
the earth, as there was no sign of inclement weather that day.
3. The frequent anecdotal reports of earthquake fog and earthquake
lights (dating back to the time of Aristotle) occurring under
cloudless skies may be explained by the electrostatic charging of
aerosol particles. In China, earthquake fog and/or earthquake lights
are frequently reported along with abnormal animal behavior (Lee et
al., 1976).
4. Many qualitative similarities are found between animal behavior
before earthquakes and before storms; this suggests that there are
common geophysical stimuli sensed by animals. It is possible that
animals could misinterpret charged aerosols of seismic origin for
electrical changes prior to an impending storm. Although animals
probably have not evolved an actual "earthquake sense" because of the
rarity of earthquakes, their "storm sense" may sometimes serve the
same purpose prior to earthquakes (Buskirk et al., 1981).

The major disadvantage with the charged aerosol hypothesis is the
lack of hard evidence. There are apparently no reliable observations
proving that the level of air ions change prior to an earthquake
(Buskirk et al., 1981).

Earthquake Gases Smelled By AnimalsIt is quite possible that some unusual animal behavior occurs as
a response to the odor of gases released prior to the occurrence of
an earthquake. The evidence that gases are released before some
earthquakes is convincing, although few quantitative data are
available for gases other than radon. If current studies suggesting
the presence of both long-term and short-term radon anomalies are
correct, the release of deep-earth gases could explain behavior
anomalies of several weeks before the event was well as several days
before. Because of technical problems, it is quite difficult to
determine quantitatively the comparative threshold of sensitivity of
animals to various odorants. Nevertheless, the available information
seems to confirm that many species of animals are remarkably
sensitive to particular odorants and that a few species, such as
dogs, seem to be more sensitive than humans for almost any olfactory
stimulus. Humans may also be culturally insensitive to strong odors
(they tend to ignore smells which they are physically capable of
detecting). In contrast, animals use their keen sense of smell to
find food, to avoid predators, and to communicate (Buskirk et al.,
1981).

CHAPTER 6
CONCLUSIONS REACHED BY RESEARCHERS

By far, the most important unanswered scientific question about
unusual animal behavior before earthquakes is, "Does it exist at
all?" A typical report is made after the event by an inexperienced,
biased, and excited observer, and no attempt is made to quantify what
constitutes "normal" or baseline level animal behavior (Buskirk et
al., 1981). Other significant factors, such as the techniques of
measurement or interview (Lott et al., 1979) and weather changes
(McClellan, 1980) are usually ignored. Otis and Kautz (1980) designed
a research program that continuously collects reports of unusual
animal behavior behavior, via a telephone hotline. Lindberg et al.
(1981) designed an outdoor animal monitoring facility that
continuously collected data indicating the level of activity by the
test animals (kangaroo rats and pocket mice). To date, these studies
have shown animal response to only small earthquakes, and there
seemed to be only slight differences in animal behavior before and
after the earthquakes.
Another important question concerning the evaluation of unusual
animal behavior in laboratory studies is, "Why would animals react to
a geophysical signal by exhibiting unusual animal behavior, and how
can they distinguish the signal from the enormous amount of
background noise?" One possible explanation is provided by a number
of physiological studies of animals suggesting that an "alerting"
stimulus makes the central nervous system more responsive to a second
stimulus. In other words, the presence of one precursory change, such
as the level of air ions, may make animals uneasy or irritable, so
that they are more likely to sense an alarm response to the sound or
vibration of a subsequent foreshock (Buskirk et al., 1981).
The variability in animal behavior reported from earthquake to
earthquake and from animal to animal has been considered an obstacle
to explaining the biological precursors. Instead, it should remind us
that different geophysical mechanisms are responsible for the
phenomena. It is not possible to generalize about abnormal animal
behavior prior to earthquakes based upon the studies of a single
animal species, nor from geophysical data from a single geographical
area (Frohlich and Buskirk, 1980).
Animals may behave "abnormally" as a result of misleading or
insufficient sensory information, misinterpretation of the available
stimuli, or a combination thereof (Kalmijin, 1980). Animals have
evolved sensory systems, from very simple to very complex, for
detecting environmental energies, and it may be assumed that this
evolution is linked to their capacity to survive. It seems unlikely
that animals have evolved sensory systems for the purpose of
detecting impending earthquakes, because it has no evolutionary
survival value. Earthquakes are simply too infrequent relative to the
life span of most animals and seldom catastrophic in terms of
population sizes (Lindberg et al., 1981). Animals do not "predict"
earthquakes; they respond to sensory input. Humans may be able to
predict earthquakes on the basis of animal responses (Verrillo,
1980). From the conclusions reached at the U.S.G.S. Conference on
Abnormal Animal Behavior Prior to Earthquakes in 1979, it is now
clear that some animals are significantly better equipped than humans
to sense almost any geophysical stimulus which may precede an
earthquake. There are many avenues for further research,
including:
1. Acoustic waves and vibrations in the frequency range 10 - 50
Hz : More measurements of animal behavior to sound both in air
and under water are needed.
2. Electric field changes and air ion monitoring : More
measurements of electric fields are needed to compare terrestrial and
aquatic environments. Monitoring equipment for changes in air ion
levels should also be set up.
3. Earthquake gases other than radon : Radon is the most
often measured gas before earthquakes; however, radon is chemically
inert, and animals probably are insensitive to it. Methane, ozone,
and sulfur compounds are likely candidates for further monitoring of
gases released prior to earthquakes.
4. Olfactory thresholds for odors : Most of the data on
animal sensitivities to natural odorants are not quantitative.
Quantitative data are necessary to test the effects of gaseous
geochemical precursors on animals.
5. Responses of common domestic animals : Dogs, cows,
horses, and chickens are the animals most commonly mentioned in the
anecdotes. Surprisingly, there have been few or no controlled studies
of the sensitivities of these animals to low-frequency sound,
vibrations, electric fields (with the exception of dogs), and odorous
gases (Buskirk et al., 1981).

The consensus of most Western researchers is that there is, as yet,
no conclusive scientific evidence for believing that abnormal animal
behavior is in any way related to the occurrence of earthquakes.
There is, however, general agreement among scientists that a great
many of the anecdotal accounts are entirely plausible in light of
what is known about animal sensory capabilities and the level of many
seismic precursors. The correlations between animal sensitivities and
the measured levels of geophysical precursors have provided
geophysicists clues about what signals they should measure to predict
earthquakes (Buskirk et al., 1981).
Although the mechanisms behind the animals' responses to seismic
precursors may not be worked out for years to come, it is possible to
use the existing information towards aiding the efforts to predict
earthquakes. For cultural and practical reasons, the Chinese have
heeded observations of abnormal animal behavior for hundreds of
years, even though they now have a nationwide seismic monitoring
network using the latest measuring instruments. China has chosen to
take anecdotal observations seriously, even if they cannot be
explained, because earthquakes have killed millions throughout her
history; false alarms are a small price and inconvenience to suffer
if many lives can be saved by warning people that an earthquake is
imminent.
It is important for scientists to cast aside prejudices held by many
skeptics against using controversial but potentially useful
information; abnormal animal behavior constitutes the largest
collection of earthquake information in existence (Tributsch, 1982).
Since the Western world relies almost exclusively on instrumental
measurements, Stewart (1977) cited the advantages of using
observations of abnormal animal behavior as a complementary part of
an interdisciplinary effort to successfully predict earthquakes.
Existing Western techniques have the following limitations: (1)
earthquakes cannot be predicted where there are no instruments; (2)
instrumental surveillance of all possible seismic areas is too
expensive; and (3) instruments cannot tell or estimate when an
earthquake will occur. Rikitake (1978) has concluded from his
statistical analysis of abnormal animal behavior that such behavior
may sometimes be used as an extremely short-term seismic
precursor.
Ongoing research may reveal additional details about sensory
capabilities and geophysical parameters, but short of controlled
observations of animals before a major earthquake, there may never be
a conclusive breakthrough that will be satisfactory to the Western
scientific establishment. The major advantage of the
interdisciplinary (biology, biophysics, geophysics, and even
psychology) approach is that the weaknesses of one discipline may be
covered by the strengths of another. There is no reason to believe
that a combined approach toward predicting earthquakes, including the
use of data on abnormal animal behavior, would be impractical. The
surge in interest in abnormal animal behavior prior to earthquakes in
the Western world was spurred by the world's first successful
short-term earthquake prediction (Haicheng, China) in 1975. Perhaps
successful results can best dictate which methods are practical or
impractical.

BIBLIOGRAPHY

An, Q. L.; Chen, X. L.; Song, S. Q.; and Gu, P.; 1987. Activities of
the Chinese Seisomological Delegation; attendance of the Second
International Earthquake Conference and visit to the United States.
Recent Developments in World Seismology, vol. 7(103), pp. 1-6.

Deng, Q.; and Jiang, P., 1981. A preliminary analysis of reported
changes in ground water and anomalous animal behavior before the 4
February 1975 Haicheng earthquake. In Earthquake Prediction: An
International Review , American Geophysical Union, Washington,
pp. 543-565.

Deshpande, B. G., 1986. Earthquakes, animals, and man; Chapter IV;
What can we do? Proceedings of the Indian National Science Academy,
Part B: Biological Sciences, vol 52, No 5, pp. 585-618.

Group of Earthquake Research (Beijing, China), 1979. Some
characteristics of behavior prior to earthquakes. In Earthquake
Prediction: Proceedings of the International Symposium on Earthquake
Prediction , Terra Sci. Publ. Co., Tokyo, Japan, pp.
243-251.

Panel on Earthquake Prediction of the Committee on Seismology, 1976.
Predicting Earthquakes: A Scientific And Technical Evaluation
With Implications For Society , National Academy of Sciences,
Washington, 62 p.

Verosub, K. L.; Lott, D. F.; and Hart, B. L.; 1981. The use of
indigenous observers to detect abnormal animal behavior prior to
earthquakes. In Baseline Studies of the Feasibility of Using
Animal Behavior as a Component in the Prediction of Earthquakes
, U.S. Geol. Survey Open-File Report 81-378, 101-115.